Gunstocks for handheld weapons date back to the sixteenth century and are derived from the Germanic word ‘stoc’, meaning tree trunk, referring to the wooden nature of the gunstock. Those early ‘hand cannons’ used a simple stick fitted into a socket in the breech end of the weapon to provide a handle for the user. Over the following centuries, gunstocks typically remained fashioned from wood, although the shape of the gunstock evolved to the gunstock of the twentieth century that is most recognizable with a butt stock for placing against a shooter's shoulder including a grip and a fore end or hand guard. Initially, gunstocks were one piece from butt to fore end, but certain weapon configurations lent themselves to two-piece stocks where the fore end was separate from the butt and grip.
The evolution of the rifle, and especially with respect to the genre of weapons categorized as assault rifles or assault weapons, has resulted in the use of gunstock hand guards that are separate from the remaining stock members. Particularly, these modern weapons are generally militarized weapons and are utilized by and mass-produced for arming of a country's armed forces. While traditional gunstocks have been machined from wooden blanks, consideration for weapon quantities, durability in adverse environments, ease of fabrication, and versatility have relegated the wooden gunstock in military weapons to the annals of history. Today's gunstocks are typically formed of metal, injection molded thermoplastic, or a combination of the two.
In particular, the separate gunstock hand guard fulfills multiple functions. The primary purpose of the hand guard is to insulate the shooter's hand from the heat of the rifle barrel. Secondly, the hand guard can include provisions for mounting accessories to the weapon such as, for example, a flashlight aligned with the barrel to illuminate the area in front of the weapon in low light or dark lighting conditions. Initially, on early rifles, such provisions were almost exclusively used for mounting telescopic sights and were thus formed on the top portion of the rifle's receiver. However, for militarized assault rifles such as the M16, these provisions are found on the hand guard and are commonly known as Picatinny rails. One or more Picatinny rails can usually be found on each hand guard. Picatinny rails (developed at the Picatinny Arsenal) are standardized, the dimensional specifications being found in MIL-STD-1913 or STANAG 2324. Hand guards can be either permanently mounted to the weapon or can be of a “quick attach/detach” design.
With normal rifles, the barrel rests in contact with the stock and in particular with the fore end or hand guard portion of the stock. If the stock is manufactured of wood, environmental conditions or operational use may shift the alignment of the stock, which, in turn, may cause the barrel to shift its alignment slightly over time. This shift can alter the flight path of the projectile and thus its impact point. Contact between the barrel and the stock also interferes with the natural frequency of the barrel, which, in some cases, can be detrimental on the weapon's accuracy. The interference of the stock with the barrel's forced oscillation as the projectile passes down the bore can cause the barrel to vibrate inconsistently from shot to shot, depending on the external forces acting upon the stock at the time of the shot. Micro-vibrations acting during the projectile's passage result in differences in trajectory as the projectile exits the bore, thus changing the downrange impact point.
One method of minimizing this detrimental interference between the hand guard and the barrel has been to free float the barrel with respect to the hand guard. Specifically, the barrel and the hand guard are each independently affixed to the weapon's receiver and project forward from the receiver in cantilevered fashion. The barrel and stock are designed to not touch at any point along the barrel's length. The barrel is “free floating” and does not contact other gun parts, other than the weapon's front sight. The free floating of the barrel minimizes possible mechanical pressure distortions of the barrel alignment, and allows vibration to occur at the barrel's natural frequency. The trend has been to outfit these weapons with free-floating barrels and hand guards. However, to maintain stability of the free floating hand guard, the attachment of the hand guard has typically been of a permanent attachment, or alternatively of a one-piece quick attach design to prevent the lateral shifting of hand guard elements with respect to each other in multiple-piece hand guards.
Single piece hand guards, even if quickly detachable, typically also require the highly undesirable removal of the front sight from the barrel in order to facilitate total removal. Conversely, quickly detachable hand guards of a multiple piece (usually two pieces) design are not free floating and are typically attached to the front end of the barrel. Therefore, a free floating, quick attach hand guard that is also stable and of a two-piece design is needed.